I didn't notice too much Spag issues in this so i'm going to break down my thoughts on each section and then talk about my overall thoughts.
Con Procs and Description:
The wording is succinct and to the point. Both sections conveys the information in an orderly manner.
Addendum 1: Discovery.
My main issue here is not the progression of events but with the dialogue of the two characters here. The characters seem to talk at the audience by describing every little thing that happens in front of them or how they are feeling. “Show do not tell”
Addendum 2-4.:
No real comments on the tests here, I think they contribute more to understanding the anomaly but I do have ordering issue with Addendum 3.
Addendum 3 happens after Addendum 4 which is not immediately apparent unless you read dates. I was confused why they were surprised that the song had any effect on people when in Addendum 3 they confirmed that the song was a part of the SCP. You should make sure all addenda are in chronlogical order.
Addendum 5.
No real complaints here, the dialogue is significantly better than in the Discovery portion.
Overall:
The main issue with this article is it's narrative. All of the addenda basically reiterate the same points of "this place is spooky and you'll die if go into it." There's no main character to speak of, or a greater intrigue to latch onto.
I was also confused to what happened to beaver as the point didn't end up going anywhere and the time dilation aspect wasn't explored in a fascinating way as it just felt like flavor text with no narrative substance.
I would suggest retooling the addenda to be about uncovering the mystery of the entities inside and the meaning behind the song that plays. You don't have to spell the whole thing out to the reader but there should be at least some clues to get some speculation in their head as to whats happening.
